Over the years, general purpose railway boxcars have progressed from relatively simple wooden structures mounted on flat cars to more elaborate arrangements including insulated walls and refrigeration equipment. Various types of railway boxcars are presently manufactured and used. A typical railway boxcar includes an enclosed structure mounted on a railway car underframe. The enclosed structure generally has an outer shell and interior paneling. The outer shell of many railway boxcars is often formed from various types of metal such as steel or aluminum. The interior paneling is often formed from wood and/or metal as desired for the specific application. For some applications the interior paneling has been formed from fiber reinforced plastic (FRP). Conventional railway boxcars are assembled from various pieces of wood, steel and/or sheets of composite materials such as fiberglass reinforced plastic. Insulated railway boxcars typically have one or more layers of insulation disposed between the outer shell and the interior paneling.
Various techniques and procedures have previously been used to satisfactorily mount or attach a roof on an enclosed structure with a typical railway car. U.S. Pat. No. 1,749,473 entitled Roof Structure shows examples of such procedures and techniques. U.S. Pat. No. 4,076,166 entitled Roof for Railway Car and Method of Making Same discloses a unitary railway car roof formed from two elongated webs of sheet metal. U.S. Pat. No. 4,275,662 entitled Railway Hopper Car Roof Support Structure shows additional examples of techniques and procedures which may be used to mount a roof on a railway car.
Many existing railway boxcars have a roof formed from galvanized steel. A typical galvanized steel roof may include ten to fifteen corrugated panels or sheets. Adjacent portions of the corrugated panels generally overlap each other. Various types of mechanical features are used to attach overlapping sometimes portions of the panels, the overlapping portions may be referred to as a "seam" or "joint" between adjacent panels. The seams or joints typically extend across the full width of the associated railway car. A seam cap is often placed over each joint between adjacent panels or sheets. The seam caps also extend across the width of the associated railway car roof.
Galvanized sheet steel is subject to rust and corrosion during the life of the associated railway car. Overlapping edges of adjacent panels or sheets and particularly the large number of mechanical fasteners at each joint may provide multiple paths for leakage of water which can damage lading carried within the interior of the associated railway car. Some estimates indicate that as much as fifty percent (50%) of all loss and damage claims related to shipping paper products in railway cars may be due to water leakage through the associated steel roof. The amount of such losses runs into millions of dollars each year.
For many years various techniques have been used to build fiberglass boat hulls. Many of these hulls have been fabricated using wet layup techniques in which each layer of material such as fiberglass or carbon fiber is first wetted with the desired resin such as polyester or vinylester and then laid in an open mold. Recently, vacuum bagging techniques have been combined with wet layup techniques to control the emission of volatile organic compounds. Vacuum bagging also produces a stronger structure by eliminating air pockets and excess resin in the finished product.
More recently, vacuum bagging techniques have been combined with an enhanced resin delivery system which allows the use of a closed molding system and dry layup of core layers and fiber reinforcing layers such as fiberglass in the mold. This process may sometimes be referred to as composite resin infusion molding. U.S. Pat. Nos. 4,902,215; 5,052,906 and 5,316,462 provide additional information concerning this type of vacuum bagging process to form a fiberglass reinforced composite article.
All patents noted in the Background of the Invention are incorporated by reference for all purposes within this application.